A copy of Ptolemy's map of the world Ptolemy was born in Egypt in about 90 AD, when the Romans were ruling Egypt. He was a Roman citizen. Probably he was the son or grandson of a Roman government slave - maybe a clerk - who was freed and got citizenship. As a boy, Ptolemy went to Greek schools in Alexandria and wrote in Greek. When [...]

Roman medicine: Galen used surgical instruments like these What do we mean by Roman medicine? Roman medicine is really West Asian and African medicine. That's because most of the great doctors of the Roman Empire lived in West Asia (in Turkey and Syria), or in Africa (in Egypt), not in Europe. Egyptian doctors [...]

Sunshine through the clouds and Earth's atmosphere You can see that the sunlight that reaches the Earth travels at different wavelengths. On a sunny day, put a full glass of water (a real glass glass) in the sunshine on your windowsill. Look where the sunshine goes through the water, and you should see rainbows on the floor or walls. [...]

Build your own model of a fusion reaction: start with a regular red lego (a proton). Wrap a rubberband around it to be the strong nuclear force. Then connect a small blue lego (an electron) to the red lego to make a hydrogen atom. Make four of these hydrogen atoms. Now imagine that your hydrogen atoms are being heated up [...]

Photons - Sunshine breaking through the clouds. When did the first photons appear? A photon is a tiny little particle of light, far too small to see individually. All light is made of photons (FOE-tahns). The earliest photons probably appeared about fifteen billion years ago, during the Big Bang. What's the speed of light? Unlike electrons and quarks, [...]

Light takes years to reach us from these stars far away in space. A light-year is the distance that light can travel in one year - that is, in the time it takes the planet Earth to make one full trip around the Sun. Light travels 186,000 miles in a second, so in [...]

Rainbow over Amazon river Light is made of billions of tiny particles called photons. These photons travel from one place to another in waves. Visible light is the subset of photons that move at a wavelength that we can see. Among the different photons that are in visible light, the ones that have the [...]

European boys at school in the 1800s In the first half of the 1800s AD, countries in northern Europe like France and Britain forced India, Ghana, Nigeria, Canada, and other countries to give them food. That meant that many people in northern Europe could stop farming and get an education. Families sent more boys to school than girls, so most of the educated people were [...]

Emilie du Chatelet, a French philosopher in the 1700s Did Emilie du Chatelet go to school? Emilie du Chatelet's rich father, who was interested in literature and science, hired tutors to homeschool her, instead of sending her to a convent school. She learned Latin, German, Greek, and Italian, as well as math and science. [...]

Any desk lamp will do for this du Chatelet light project What is the du Chatelet light project? Emilie du Chatelet was a scientist who lived in France in the 1700s, in the time of Louis XV. She proposed this experiment as a way of showing that longer wavelengths of light heat things [...]

Advertisement

Sponsor this article!

More great articles/no distracting ads? Sign me up! Just $1.00, with daily blog posts! So far, 69 articles have found sponsors - 2431 more sponsors needed!
Join our Patreon community
Together we can build a great community and a great website.

Advertisement

Spam Blocked

About

Since 1994, Quatr.us Study Guides has offered free history and science articles to keep you connected to the latest discoveries in world history. We want you to know why things happened, how that matters today, and what you can do about it. Experts write all our 2500 articles (and counting!), with full bibliography and citation information. Coming soon: free lesson plans and a first-rate resource area.

Why are we called Quatr.us?

Good question! We were thinking of the four corners of the world - four Quarters. We were thinking of Questions, and Quick, and Quality. We wanted a name that would be ours and nobody else's.

Get in touch!

We’d love to talk! Reach out on twitter (@Quatr_us) or Instagram (@quatr.us) or by email (karen @ quatr.us). Open to your sponsorships, link exchanges, or just friendly talk about history. I’d be up for guest posts on your blog, joint Twitter threads, lesson plans, book reviews, or what-have-you. Send all your ideas!